The invention relates to an inspection device having an inspection head that is movable in at least two directions relative to a guide carrier that supports a substrate that is to be inspected, whereby the substrate has at least one printed-one layer, whereby the inspection head has an illumination mechanism and a detection device that detects the electromagnetic radiation reflected from the substrate and conveys it to an evaluation device for detecting errors of the substrate.
Such an inspection device is used to test the quality of circuits that in particular are placed or deposited using thick target or layer technology. Such circuits are ordinarily applied in a plurality, for example 20, of layers via screen printing technology. In this connection, it is important that layers containing errors, for example due to mask errors, not be applied.
To check for this, it has become known to test a function of the circuit individually by means of electrical test equipment. The drawback of this is that almost all of the layers have to be applied, and then the testing is undertaken. If the test shows errors, then there is only the possibility of throwing the pertaining chip away, which is accompanied by corresponding cost disadvantages.
It has furthermore also been proposed that optical testing be undertaken during the application of the layers. This can be effected, for example, visually, in other words by a trained operator. However, it has also become known to detect or capture the image of the printed layer or layers via suitable optical detection devices, and to compare the image with a desired image. If the deviation is then too great, the pertaining chip is eliminated.
Numerous approaches have become known in which such inspection devices can be realized and improved. One example is U.S. Pat. No. 4,389,669. With this approach, an optical testing is undertaken using an optical detection device, namely a microscope, accompanied by the use of a camera; in principle, this testing is also suitable for the handling of chips. However, with the customer requirement of a rapid and reliable testing of the electronic circuits or chips, this approach requires a considerable capital outlay for equipment.
A further example for detecting or handling electronic circuits via cameras is disclosed in U.S. Pat. No. 5,245,421, whereby pursuant to U.S. Pat. No. 5,060,065, special illumination devices can also be used to improve the detection possibilities.
Finally, it is known from U.S. Pat. No. 4,673,988 to realize an inspection device using an image that is divided into image areas. This takes place via the image processor that is provided, whereby the object that is to be inspected is movable in two dimensions.
The aforementioned approaches have the common drawback that a relatively great capital expenditure is required, yet an evaluation speed is still to be desired, especially if a plurality of layers of a chip are to be tested. In addition, the precision of detection of the known approaches needs improvement, especially for conceiving an inspection device for a rapid throughput at a low definition, yet where a more precise detection with a specific series of chips is to be undertaken.
It is therefore an object of the invention to provide an inspection device of the aforementioned general type that is further improved with regard to the throughput, and also the precision of detection and the reliability of detection, whereby it should also be possible to have a flexible adaptation to varying requirements.